The interactive effect of long nighttime sleep and daytime napping on QTc prolongation in hypertensive adults

Prolongation of the corrected QT interval (QTc) reflects delayed ventricular repolarization and predisposes patients to malignant arrhythmias and sudden cardiac death. Hypertension is strongly associated with QTc abnormalities, yet the influence of habitual sleep patterns remains underexplored. We conducted a cross-sectional analysis of 1,338 hypertensive participants from the Fasa Adult Cohort Study. Sleep parameters were assessed using the Pittsburgh Sleep Quality Index, and 12-lead electrocardiograms were obtained under standardized conditions. QTc was calculated using Bazett’s formula, with prolongation defined as > 450 ms in men and > 460 ms in women based on the latest AHA/ACCF/HRS recommendations. Logistic regression models, adjusted for demographic, clinical, and medication-related confounders, evaluated associations and interactions between sleep behaviors and QTc prolongation. QTc prolongation was observed in 20.5% of participants. While prolonged nighttime sleep (≥ 9 h) and daytime napping alone were not independently associated with QTc prolongation, their combination significantly increased the risk (OR = 3.54; 95% CI: 1.29–9.71; p = 0.014). Interaction analysis confirmed a statistical interaction between prolonged night sleep and regular napping (OR = 4.36; 95% CI: 1.43–13.27; p = 0.009), independent of antihypertensive medication use. Conversely, short nighttime sleep (≤ 6 h) accompanied by daytime napping showed no statistically significant association with QTc prolongation; with point estimate suggesting lower odds. Excessive total sleep duration, distributed across both night and day, is strongly associated with QTc prolongation in hypertensive adults. This combined sleep phenotype may represent a novel behavioral risk factor for impaired cardiac repolarization, highlighting the importance of incorporating sleep assessment into cardiovascular risk stratification. Moreover, hypertensive individuals with long nighttime sleep may mitigate their risk of QTc prolongation by reducing additional daytime naps, potentially lowering the likelihood of arrhythmic events. These findings identify a sleep phenotype associated with QTc prolongation and highlight the need for longitudinal studies to clarify causality.